Nitrogen-Doped Titanium(IV) Oxide Particles as a Visible-Light-Responsive Photocatalyst Prepared from Exfoliated Titanate Nanosheets

Nitrogen-doped titanium(IV) oxide (NT) particles were synthesized from titanate nanosheets prepared by exfoliation of lepidocrocite-like layered titanic acid using tetrabuthylammonium hydroxide. The layered composites of nanosheets with ammonium ions intercalated in the interlayer spaces, which were prepared by treatment of the nanosheets with a solution containing ammonium ion at room temperature, were transformed to anatase crystallites of titanium(IV) oxide (TiO(2)) by calcination in air at 723 K. The powders exhibited a yellow color corresponding to photoabsorption in the visible region (400-500 nm) presumably due to generation of a localized dopant level within the band gap. Incorporation of nitrogen anion species was confirmed by N Is X-ray photoelectron spectroscopy. In the case of visible light irradiation (> 400 nm), the NT particles showed photocatalytic activity for oxidative decomposition of acetic acid in the presence of iodate anion (IO(3)(-)) as an electron acceptor, while a commercial TiO(2) showed no photocatalytic activity under similar photoirradiation conditions. The fact that the photocatalytic reaction occurred negligibly over NT particles in the absence of IO(3)(-) indicates that IO(3)(-) acts as an electron acceptor in the visible-light-induced photocatalytic reaction and retards recombination of photogenerated carriers in the NT particles.